# Meet the zeptosecond, the shortest unit of time ever measured

#### David J Franks

Can somebody please check, it says that a zeptosecond is 21 zeros followed by 1. I think a zeptosecond is 10 to the - 21 seconds, that would mean 20 zeros followed by a 1.

UPDATE - I'm not going mad, the article has now been corrected, see footnote to the article. (I'm not going mad, I'm not mad, I'm not going mad, I'm not going mad, I'm not going mad)

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#### Wm. A. Garrett

I am no expert, but I believe that in a sense you both are correct, as they are counting the zero to the left of the decimal point which generally (and logically) is not done.

#### danr2222

I am no expert, but I believe that in a sense you both are correct, as they are counting the zero to the left of the decimal point which generally (and logically) is not done.
"or a decimal point followed by 21 zeroes and a 1"

That is clearly not what they are doing. We may pretend to consider what they were thinking, but that is by no means betrayed by the wording.

David J Franks

#### mntom

I always thought a zeptosecond was the amount of time it took a New Yorker to honk the horn at you when the light turns green.

#### kamikrazee

Roughly the attention span of several well-known politicians.

#### mhartry

Just a minor correction. Hydrogen has 1 proton and 1 electron. Helium has 2 protons, 2 neutrons, and 2 electrons.

#### Calerdine

Just a minor correction. Hydrogen has 1 proton and 1 electron. Helium has 2 protons, 2 neutrons, and 2 electrons.
The analysis discusses a hydrogen molecule, which consists of two hydrogen atoms; the molecule does contain two protons and two electrons. Upon first reading I made the same mistake. The are using molecules so they knock one electron out of each of the closely spaced atoms.,

#### Tripd

Can somebody please check, it says that a zeptosecond is 21 zeros followed by 1. I think a zeptosecond is 10 to the - 21 seconds, that would mean 20 zeros followed by a 1.

New user here, I just signed up to answer this after finding nothing on the net.

From Wikimedia (what about that, a nice html table!)

In words
(long scale)
In words
(short scale)
Prefix (Symbol)DecimalPower
of ten
Order of
magnitude
trilliardthsextillionthzepto- (z)0.00000000000000000000110−21−21

Table too big, but anyway, there's zepto! 21 places.

#### David J Franks

New user here, I just signed up to answer this after finding nothing on the net.

From Wikimedia (what about that, a nice html table!)

In words
(long scale)
In words
(short scale)
Prefix (Symbol)DecimalPower
of ten
Order of
magnitude
trilliardthsextillionthzepto- (z)0.00000000000000000000110−21−21

Table too big, but anyway, there's zepto! 21 places.
The article has now been corrected to contain 20 zeros after the decimal point followed by1. See footnote to the article.

#### CVAngelo

So just to clarify ... I'm almost 2 trillion trillion billion zeptoseconds old? Thank goodness for that. I thought I might have been over the hill.

David J Franks

#### mhartry

Okay. Got it. Thanks.

#### Wm. A. Garrett

"or a decimal point followed by 21 zeroes and a 1"

That is clearly not what they are doing. We may pretend to consider what they were thinking, but that is by no means betrayed by the wording.
"or a decimal point followed by 21 zeroes and a 1"

That is clearly not what they are doing. We may pretend to consider what they were thinking, but that is by no means betrayed by the wording.
Yes, you are correct, and the article was clearly wrong. I was trying to cut slack...probably not a good thing regarding a scientific paper.

#### Wm. A. Garrett

Clearly, they need a Prefrooder.

#### Hayseed

If one could switch a hard x-ray laser just a little quicker, we could strobe an electron with a frequency difference in the visual range, and watch it.

#### David J Franks

It may help to put this measurement in perspective by changing the units to attoseconds ie 10^-18 seconds. The time now becomes .247 attoseconds to cross the molecule of hydrogen. This compares with one tick on the worlds best atomic clock, which is 10^-19 seconds or .1 attoseconds! So, it takes 2.47 ticks to cross the molecule of hydrogen. Phew! not so fast after all

"Given that our best atomic clocks agree with one another and can measure ticks as small as 10^(minus19) seconds, or a tenth of a billionth of a billionth of a second"

from;

https://www.livescience.com/what-ar...at our best atomic,19 in the journal Physical

All the above posts should not distract from what is a truly astonishing measurement.

#### Valentine Michael Smith

So, not the shortest time measured. Need a bigger edit.

"But with the aid of machine-learning algorithms, the researchers showed that this tiny crop of unexplained muons has just a 0.27% of emerging by random chance."

@David J Franks :

David J Franks

#### .308Lapua

Just take all this zepto business with a grain of salt ~ they are just splitting hairs.

Zepto, wasen't he one of the Marx Brothers?

#### Green1971

When that measurement was taken, at what velocity/rate was the universe expanding at the location of the measurement? Rhetorical question. I asked the question to imply that time is variable. Even the smallest measurement of time is inaccurate because everything in this universe is in constant motion. Our use of linear time scales create problems. We've seen this as time slows down the closer we approach the speed of light. Just some thoughts on the subject...

David J Franks

#### David J Franks

When that measurement was taken, at what velocity/rate was the universe expanding at the location of the measurement? Rhetorical question. I asked the question to imply that time is variable. Even the smallest measurement of time is inaccurate because everything in this universe is in constant motion. Our use of linear time scales create problems. We've seen this as time slows down the closer we approach the speed of light. Just some thoughts on the subject...
To the best of my knowledge, I don't think space is expanding inside galaxies because the force of gravity is stronger than the force expanding the universe. I think it is only the space between galaxies that is expanding. Likewise, the force which holds atoms and molecules together is also much stronger than the force expanding the universe, so I don't think it would interfere with the experiment.

As for the effects of relativity, the experiment and the experimenter are in the same frame of reference and are moving at the same speed relative to each other, so I don't think that will make any difference either. Since the laws of physics are the assumed to be the same throughout the universe then I assume you will get the same answer for the experiment anywhere in the universe and at any stage in in its expansion.

#### Stan

As for the effects of relativity, the experiment and the experimenter are in the same frame of reference and are moving at the same speed relative to each other, so I don't think that will make any difference either. Since the laws of physics are the assumed to be the same throughout the universe then I assume you will get the same answer for the experiment anywhere in the universe and at any stage in in its expansion.
This just reminded that it might be worth a mention that as our measure of distance is interchangeable with time ( 1 sec = approx 300,000km) then the shortest time would be equivalent to the shortest distance. perhaps the Planck Length. I'll let you do the maths equivalent
Probably a lot smaller yet.

#### dodster

Since the laws of physics are the assumed to be the same throughout the universe

Surely this statement is incorrect, time is affected by gravity

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