Ask Me Anything AMA with Astrophysicist Dr. Joe Pesce!

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DrJoePesce

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Hello everyone!

My name is Dr. Joe Pesce. I'm an astrophysicist primarily interested in the environments of the galaxies hosting supermassive black holes (also known as Active Galactic Nuclei). I've worked with clusters of galaxies, and the atmospheres of giant and supergiant stars.



Currently, I'm a Program Director at the National Science Foundation (NSF), Division of Astronomical Sciences, responsible for the National Radio Astronomy Observatory (NRAO); a part-time Professor at George Mason University in Fairfax, Virginia; and a Visiting Professor at the University of Colorado, Boulder, Colorado. And I'm a Fellow of the Royal Astronomical Society. Oh - and I LOVE all things Star Trek!!

I’m looking forward to this AMA and to hearing from you with your questions about astronomy! I will try to answer as many as possible.

I have a broad understanding of the field, but it’s vast (one could even say “astronomically” large), so I might need some time to find the answer.

Also, there may be lots of questions I can’t answer, because I don’t know – and maybe the answer isn’t yet known (that’s a fun part about astronomy – lots of unknowns still). Please keep this in mind.

Astronomy is exciting, and we live in an exciting time for the field. Thank you for letting me share it with all of you!

Dr Joe

Any opinions, findings, conclusions or recommendations presented in this responses are only those of the author and do not necessarily reflect the views of the U.S. National Science Foundation.
 
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SHaines

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Welcome back to the forums! It's very exciting to have you join us again.

I have a question that's theoretical, but I'm just curious where you stand. If you had the ability to pick an area of the universe at random and get all the data you can imagine from it, would you pick a spot out on the edge of the expanding universe to see how things work there, or would you grab something near the universal origin point?

I suspect these two areas would have the most dramatic differences, but I could be very wrong, so whatever other option you can think of would be welcome too.

Thanks!
 

DrJoePesce

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Mar 27, 2020
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Welcome back to the forums! It's very exciting to have you join us again.

I have a question that's theoretical, but I'm just curious where you stand. If you had the ability to pick an area of the universe at random and get all the data you can imagine from it, would you pick a spot out on the edge of the expanding universe to see how things work there, or would you grab something near the universal origin point?

I suspect these two areas would have the most dramatic differences, but I could be very wrong, so whatever other option you can think of would be welcome too.

Thanks!
Thank you!

Great question - Difficult question!

Will you allow me to travel in time too? If so, I would pick the Big Bang event and, I don’t know, maybe the following 250 million years. That would be very interesting, and of all the things we don’t know well, probably the period that we know about least. Outside of a time context, there is not really an origin point; nor is there an edge.

Going beyond your question, I would like to visit one of my objects of research – blazars, or any active galactic nucleus – to see what is really happening there.
 
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Aug 30, 2020
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Hello,
My son saw an extremely bright object 2 mornings ago; and I saw it yesterday at approx 5 am. It was approx 60 to 70 degrees up in the shy E.N.E. This morning there was nothing there. It looked like a supernova event but I have not been able to find any reference to it. I live in North West Brittany, France. Any ideas as to what this was.
 
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DrJoePesce

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In your opinion, which of the modern Sci-fi films has gotten the most right in terms of the science?

Hello Meicy - Wow, an even more difficult question!

I can’t claim to have a definitive insight into a large number of science fiction films. In general, those with scientists as advisors are going to be a good bet for being close to getting things right. I thought the Martian did a pretty good job (though my planetary science colleagues also note some issues). I think Interstellar was pretty good. And, in my opinion, a scene that is fantastic for shear emotion is that in Passengers when Chris Pratt goes out on the tether and views the majestic Milky Way all around him. This scene really gives the sense of being IN the galaxy. I’ve encountered this emotional feeling when viewing the Milky Way from a truly dark site, and from the Southern Hemisphere, in particular. (By the way, great early science fiction film, maybe one of the best in my opinion, is Forbidden Planet.)

Modern science fiction films are, generally, pretty good about the science – because they have to be: The audience is pretty science savvy these days, and because directors and producers care about getting the science right (in my experience). But even the best science fiction film is going to get things wrong at some level: Because sometimes nature is boring and they need to spice things up a bit and, because, hey, it’s science FICTION!
 

DrJoePesce

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Mar 27, 2020
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Hello,
My son saw an extremely bright object 2 mornings ago; and I saw it yesterday at approx 5 am. It was approx 60 to 70 degrees up in the shy E.N.E. This morning there was nothing there. It looked like a supernova event but I have not been able to find any reference to it. I live in North West Brittany, France. Any ideas as to what this was.
Hello Breton Prof!
My son saw an extremely bright object 2 mornings ago; and I saw it yesterday at approx 5 am. It was approx 60 to 70 degrees up in the shy E.N.E. This morning there was nothing there. It looked like a supernova event but I have not been able to find any reference to it. I live in North West Brittany, France. Any ideas as to what this was.

I can’t say definitively but I suspect it is Venus. Venus is currently very bright in the pre-dawn sky, and tomorrow (1 Sep), it’s about 30 degrees above the East horizon one hour before sunrise (which should be about 6:30am). It does move, of course, so is going to be a slightly different location from day to day. Good guess on supernova, but a supernova visible to the naked eye like that would be news indeed! And wouldn’t fade away in a couple of days.
 
Feb 28, 2020
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Hi Dr. Joe Pesce,

I'm interested in getting to the bottom of reality. Do you know what space consists of? I hear things such as quantum foam, quantum fields, vacuum energy, dark energy, aether. Are any of these correct or are they all the same?

Secondly, whatever space is, what's happening to it as the universes expands? Is something getting more dilute, is it getting more stretched, are those grid lines we see in diagrams moving further apart?

Thirdly, again whatever space is, is it on average stationery throughout the universe, ie is it an absolute frame of reference?

Thank you :)
 
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Aug 31, 2020
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Hi Dr Pesce,

I have become increasingly fascinated by science over the years and have in fact written three books on the subject, the latest of which is titled: “The Electromagnetic Universe”. (Available on Amazon) One of the troublesome aspects of present day main-stream physics is that we do not have a cohesive interpretation of what heat actually is. Sure heat is caused by vibrations is one explanation but going deeper into the subject on the level of Max Planck and Black Body radiation, we are given the impression that all heat comes in the form of electromagnetic radiation. Is this true? Most probably but according to my theory it manifests in two ways. The first is by direct emission of photons by agitated electrons, this is the high frequency high energy heat. But, what happens at the lower levels past the infra-red. I have a novel theory, and it goes like this. We are aware from looking at the working of atomic clocks that Caesium 133 atoms are radiated with microwave radiation at a frequency of 9 192 631 770 Hz , that the radiated electrons in the Caesium 133 atoms do not immediately reciprocate with electromagnetic radiation of the same frequency. Instead the valence atoms in the hyper fine structure of the Caeisum 133 atom begin to oscillate at 9 192 631 770 Hz, but this does not result in these electrons producing radiation of 9 192 631 770 , instead the whole atom is affected and they enter a metastable stable state. The reason is that frequency in the micro-wave range does not have enough energy to enable, the electron to directly re-radiate it. Instead it is my theory that electrons are so volatile that when the caesium 133 atoms are irradiated with a frequency of 9 192 631 770 Hz some electrons leave the atom and start to emit what I term as ‘conduction’ photons this results in the setting up of micro and nano currents. It is these micro and nano currents that re-radiate the original 9 192 631 770 Hz frequency and others.

Now finally to my question, the Cosmic Microwave Background Radiation is found throughout the Universe but with what is it reacting? The Universe has a density of about one atom in every cubic centimetre of space. So what is the CMBR reacting with? To state that it is relic energy from the Big Bang seems to me to be the height of absurdity. Instead I think what is responsible for the CMBR are micro and nano currents set up throughout the Universe. Electrons are very volatile, wave a conductor and the electrons will be disturbed. Pick up a pencil from a desk and millions or is it trillions of electrons will be moved around. My feeling is that it is this volatility that accounts for the CMBR. It is radiation that shows the vitality of the Universe now today, not from the time of the Big Bang. Yet it is apparent that the CMBR is reacting with something. To find out what (I think) is reacting with the CMBR, you must read my theory: https://www.academia.edu/37258409/The_Electromagnetic_Universe_docx
 
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Sep 1, 2020
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Would there be any measurable distinction if a distant galaxy were made of antimatter?

Would a universe where the components contract as it cools look the same as a universe where the totality cools as it expands?
 
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DrJoePesce

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Hi Dr. Joe Pesce,

I'm interested in getting to the bottom of reality. Do you know what space consists of? I hear things such as quantum foam, quantum fields, vacuum energy, dark energy, aether. Are any of these correct or are they all the same?

Secondly, whatever space is, what's happening to it as the universes expands? Is something getting more dilute, is it getting more stretched, are those grid lines we see in diagrams moving further apart?

Thirdly, again whatever space is, is it on average stationery throughout the universe, ie is it an absolute frame of reference?

Thank you :)
Hello David J Franks. The short answer to your first question is, no, not really! All of those things you mention are probably part of what makes up “space”, but what does that mean?

The other questions are just as problematic, but maybe a bit easier to answer: As the universe expands, space expands – it is the “substance” that is expanding. So space is getting bigger (I can’t tell you what is happening at the smallest – quantum – scale, but presumably that scale is expanding too. But remember that - at least “today” – while the expansion is happening everywhere, on the local scales the expansion is minimal (the expansion rate is ~70 km/s PER megaparsec (a megaparsec is about 3.3 million light years). That means we can see distant galaxies moving away, but we don’t see our cup of coffee moving away. Space around us is expanding too, but at the subatomic scale (so the cup of coffee IS moving away from you, just not in a measurable way). In the future, as expansion continues, it will become more obvious even on the smaller scales.

As the universe expands and gets bigger, matter gets “diluted” – that is, the density of matter decreases. And yes, space is expanding or stretching.

Perhaps at the quantum level space is “stationary”, but I think not.
 
Mar 25, 2020
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Hello David J Franks. The short answer to your first question is, no, not really! All of those things you mention are probably part of what makes up “space”, but what does that mean?

The other questions are just as problematic, but maybe a bit easier to answer: As the universe expands, space expands – it is the “substance” that is expanding. So space is getting bigger (I can’t tell you what is happening at the smallest – quantum – scale, but presumably that scale is expanding too. But remember that - at least “today” – while the expansion is happening everywhere, on the local scales the expansion is minimal (the expansion rate is ~70 km/s PER megaparsec (a megaparsec is about 3.3 million light years). That means we can see distant galaxies moving away, but we don’t see our cup of coffee moving away. Space around us is expanding too, but at the subatomic scale (so the cup of coffee IS moving away from you, just not in a measurable way). In the future, as expansion continues, it will become more obvious even on the smaller scales.

As the universe expands and gets bigger, matter gets “diluted” – that is, the density of matter decreases. And yes, space is expanding or stretching.

Perhaps at the quantum level space is “stationary”, but I think not.
So is the coffee cup moving away from us, or is all the matter within the cup and me moving away from itself, too?
 
Aug 31, 2020
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Would there be any measurable distinction if a distant galaxy were made of antimatter?

Would a universe where the components contract as it cools look the same as a universe where the totality cools as it expands?
Surely , if such a situation were true, it would make for a very twisted rendition of the second law of thermodynamics
 
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Dec 23, 2019
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Was it necessary for us to be in a black hole for the physics to be right? For decoherence and wave collapse to be functional? For gravity to be the right strength? For dark matter and energy to be what it is?

Doesn't the Schwarzschild Radius and the Holographic Principle hint we are in one? Could our parent black hole be different than the ones with us? Could physics be encoded in the holographic projection? Haven't we questioned how physics magically has the correct settings to allow life?

Is the acceleration of the universe from our parent black hole feeding which causes more quantum information/energy into the whole system? Would this mean our parent Universe only has one Black Hole that is constantly feeding? If physics is different there, could it be a diet of never-ending quantum waves?

Is the Big Bang and Cosmic Inflation from the initial formation of our parent black hole?

Are there layers to spacetime? Matter flows on time, space, and gravity. Is the matter layer made of quantum information? Does time dilation occur with information density? Is dark matter, information that imprinted before annihilation?

Is the formation of a Black Hole from Dark Matter forming from annihilation that occurs in a collapsing star? Is gamma-ray bursts from this annihilation? Could gamma-rays be information escaping a Black Hole?
 
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DrJoePesce

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Would there be any measurable distinction if a distant galaxy were made of antimatter?

Would a universe where the components contract as it cools look the same as a universe where the totality cools as it expands?

Hi Cam B!

Thanks for the questions.

An antimatter galaxy: No, it would be just like a galaxy made of matter. The problem is it would have to be entirely isolated from matter (or the matter/anti-matter would annihilate themselves). This is theoretically possible, I guess, but practically impossible, or certainly very difficult. It’s unlikely a pocket of antimatter could be isolated so as not to interact with matter and be destroyed.

Contracting and expanding universes. As the universe expands (our current universe), we see the photons left over from a period shortly after the Big Bang as they are cooling (explicitly they are losing energy as they fly through the expanding universe). In the far distant future, the universe as a whole “cools” because the material to make stars will be too far apart to collapse as stars, and eventually the stars die, matter gets spread out, and everything trends toward absolute zero.

If the universe is able to contract, become smaller, as it gets smaller and matter gets pushed closer and closer together, it will heat up, eventually to tremendously high temperatures. This sort of universe could form a singularity and then have another Big Bang-like event. (Our universe probably will not do this.) If our universe were contracting today, the difference would be that the galaxies would all be moving towards us, instead of away from us.
 
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DrJoePesce

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So is the coffee cup moving away from us, or is all the matter within the cup and me moving away from itself, too?
Good morning jchamot!

All the matter within the cup and you are moving apart. We are all "embedded" in space and space is expanding. It's just that on the smallest scales (for now), the expansion rate is miniscule.
 
Sep 2, 2020
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Hi there!

So, the universe is made up of galaxies and galaxies are made up of stars. Do we have some sense of what exists between galaxies? Is it literally just empty space, or do things like nebula and other celestial phenomena all happen within the star-rich environment of galaxies?
 
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Feb 28, 2020
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Hi Dr. Joe Pesce (again)

Thanks so much for your last reply:)

Below is a copy of my post to another thread, but no one answered it, so I would like your opinion, please;


"Space is a 'something' it's not a void. Its been called aether, quantum foam, quantum fields, vacuum energy, space-time fabric, dark energy etc. I'm not sure which is correct. Gravity can distort it. It's almost substance like. Even the video called it a ball of space (and energy). So why can't the big bang bang be called an explosion of 'space'?

The accepted view is that galaxies are not moving through space, it's that the space between galaxies is expanding.

If I make a ball of explosive and pack it with ball bearings, and detonate it, the ball bearings can be analogous to galaxies and the hot exploding gas analogous to expanding space. I can equally say here, that the ball bearings are not moving through the hot gas, but instead, it's the hot gas between the ball bearings expanding.

Also, galaxies are not held in place by space, because some have a blue shift and are coming towards us. The same in the bomb, the ball bearings are not held in place by the hot gas."


It seems to me that space doesn't have a hold on galaxies, so are galaxies flying apart as in an explosion, independently of space expanding? Last-minute thought, if space has no hold on galaxies how come the speed of galaxy recession is accelerating? does that mean dark energy is also independent of space?

My question to you, please, is what is the difference between an explosion and an expansion? Why can't I treat the Big Bang as an explosion of space?

Thank you :)
 
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May 6, 2020
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What are your thought on gravitons ? Why is there the thought that the mechanism of gravity would work via particles ? Also hypothetically, if an immense black hole just 'popped' into existence 4 light years away from me, would the gravity of the black hole take 4 years to affect me ? or would the effect be instantaneous with the appearance of the black hole? Is there any experimental evidence of the 4 year or /instantaneous effect?
 
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DrJoePesce

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In responding to a post, I got to thinking about things I would like to know more about in astrophysics. We know a lot about a lot of things in astronomy – much more than when I was a graduate student long ago. And it seems like not a day goes by without a new, neat, astronomical observation making the news. And keep an eye and ear open: NSF’s newest astronomical facilities – the Daniel K Inouye Solar Telescope and the Vera C. Rubin Observatory – will soon be coming online, and they promise some truly spectacular (game changing) science. Even given this, astronomy is very much still in discovery space: new observations lead to completely unexpected findings all the time.

Of course, I’m a scientist, so I want to know everything! But let me try to narrow it down to a random (short) list of neat things I’d like to see:
  • What’s driving the solar cycle
  • What are Fast Radio Bursts
  • Is there extraterrestrial life
  • What is Dark Matter
  • What is Dark Energy
  • More info about supernovae
  • How do galaxies form
  • Why are there different types of galaxies
  • What happened immediately after the Big Bang
  • How do supermassive black holes form and grow
  • What are AGN
  • How do AGN jets remain powered for such large distances and long times
  • How do stars and planets form
  • Is there a unified model at work in the universe
  • Are the laws of nature truly universal in space and time
  • What will happen to the universe in the deep future
  • What is happening in the quantum realm
  • What happens inside the event horizon of a black hole
 
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DrJoePesce

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Mar 27, 2020
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Hi there!

So, the universe is made up of galaxies and galaxies are made up of stars. Do we have some sense of what exists between galaxies? Is it literally just empty space, or do things like nebula and other celestial phenomena all happen within the star-rich environment of galaxies?
Hello RoddenberryStan5!

Almost certainly there is stuff between the galaxies; it’s not completely empty space.
But the density is low, it's probably cold, so it's hard to see. We have found rogue stars between the galaxies, and there’s certainly gas and dust.
 
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Dec 23, 2019
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I represent the new age of physics ..I understand why you are too afraid to answer any of my questions ..it turns everything you know on its head.
 

DrJoePesce

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Mar 27, 2020
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Hello RoddenberryStan5!

Almost certainly there is stuff between the galaxies; it’s not completely empty space.
But the density is low, it's probably cold, so it's hard to see. We have found rogue stars between the galaxies, and there’s certainly gas and dust.
P.S. Do I dare to hope there is a connection to the Great Bird of the Galaxy?
 
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DrJoePesce

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Mar 27, 2020
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Hi Dr. Joe Pesce (again)

Thanks so much for your last reply:)

Below is a copy of my post to another thread, but no one answered it, so I would like your opinion, please;


"Space is a 'something' it's not a void. Its been called aether, quantum foam, quantum fields, vacuum energy, space-time fabric, dark energy etc. I'm not sure which is correct. Gravity can distort it. It's almost substance like. Even the video called it a ball of space (and energy). So why can't the big bang bang be called an explosion of 'space'?

The accepted view is that galaxies are not moving through space, it's that the space between galaxies is expanding.

If I make a ball of explosive and pack it with ball bearings, and detonate it, the ball bearings can be analogous to galaxies and the hot exploding gas analogous to expanding space. I can equally say here, that the ball bearings are not moving through the hot gas, but instead, it's the hot gas between the ball bearings expanding.

Also, galaxies are not held in place by space, because some have a blue shift and are coming towards us. The same in the bomb, the ball bearings are not held in place by the hot gas."


It seems to me that space doesn't have a hold on galaxies, so are galaxies flying apart as in an explosion, independently of space expanding? Last-minute thought, if space has no hold on galaxies how come the speed of galaxy recession is accelerating? does that mean dark energy is also independent of space?

My question to you, please, is what is the difference between an explosion and an expansion? Why can't I treat the Big Bang as an explosion of space?

Thank you :)
Hello Again David J Franks!

So, an explosion isn’t really a perfect analogy, but it’s okay. It’s just that most of the energy of the Big Bang goes into the expansion of the universe – space, as you say. That expansion – on the large scale – is overwhelming. And while individual galaxies and objects embedded in space can move independently of the cosmic expansion (for example our Milky Way galaxy and the Andromeda galaxy are falling into each other), the expansion will win in the end. In the far distant future, expansion will have an affect even on the smallest scales, and atomic nuclei, for example, will be pulled apart by the expansion.

One reason the explosion analogy doesn’t, fully, work, is because SPACE is expanding (imagine the rubber sheet stretching). In an explosion, while a gas might be expanding (for example), that’s not the same thing as the medium in which everything is embedded is itself expanding.
 
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