# The Naked Scientists Forum

### Author Topic: How fast do atoms travel?  (Read 18292 times)

#### Yasser

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##### How fast do atoms travel?
« on: 19/12/2008 09:16:20 »
Dear Naked Scientists,

At what speed, preferably in metres per second if applicable, does an atom travel from point a to point b and does this speed fluctuate or is it constant?

Warm Regards,

What do you think?

#### chris

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##### How fast do atoms move?
« Reply #1 on: 19/12/2008 22:40:18 »
The answer depends upon the temperature. At absolute zero they don't move at all. As more energy enters the system the average kinetic energy of the particles increases; that is they begin to move more quickly. But the key is the word "average" because some particles will have lots of energy, some much less - this is why water still evaporates even at less than boiling point because some molecules gain enough energy to leave the liquid and enter the gas phase.

Therefore it's very difficult to say how fast atoms move because there is no hard and fast answer.

Chris

#### RD

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##### How fast do atoms move?
« Reply #2 on: 19/12/2008 22:59:28 »
Not all molecules in a substance have the same kinetic energy:
their speeds are described by a bell-shaped graph: the Maxwell–Boltzmann distribution...

Quote
The speed probability density functions of the speeds of a few noble gases at a temperature of 298.15 K (25 °C). The y-axis is in s/m so that the area under any section of the curve (which represents the probability of the speed being in that range) will be unitless.

http://en.wikipedia.org/wiki/Maxwell-Boltzmann_distribution

#### Soul Surfer

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##### How fast do atoms move?
« Reply #3 on: 19/12/2008 23:45:43 »
Those graphs give a good indication of the speeds of typical atoms at room temeperature note there are a significant number of helium atoms going faster than 2.5Km/sec or about one quarter of the escape velocity.

It is also interesting to note that atoms in solids are also moving at similar speeds but in an oscillatory manner.

also  the mean free path of atoms in air is around 60 nanometres.  bearing in mind that atoms are about one quarter of a nanometre across an atom in gas at atmospheric pressure and room temeperature will only mov a a couple of hundred times its own width before it hits another atom
« Last Edit: 19/12/2008 23:52:10 by Soul Surfer »

#### RD

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##### How fast do atoms move?
« Reply #4 on: 20/12/2008 18:22:36 »
The speed of sound in a gas can give you an approximation of the average speed of the molecules ...

Quote
Sound generally travels at about 70% of the mean molecular speed in gases
http://en.wikipedia.org/wiki/Speed_of_sound#Effect_of_frequency_and_gas_composition

#### labview1958

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##### How fast do atoms travel?
« Reply #5 on: 23/12/2008 11:24:52 »
Atoms do no move at absolute 0? How about electrons orbiting the atom? Are they not moving at absolute 0?

#### DoctorBeaver

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##### How fast do atoms travel?
« Reply #6 on: 23/12/2008 11:38:22 »
Atoms do no move at absolute 0? How about electrons orbiting the atom? Are they not moving at absolute 0?

No. If electrons are moving then they have energy. To get to absolute zero there would have to be no movement, and that is impossible.

#### Bored chemist

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##### How fast do atoms travel?
« Reply #7 on: 23/12/2008 11:43:55 »
Atoms and electrons jolly well do move at absolute zero. If they didn't it would be a breach of the uncertainty principle.
This movement is the zero point energy (about which an enormous amont of nonsense is talked).

#### DoctorBeaver

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##### How fast do atoms travel?
« Reply #8 on: 23/12/2008 11:46:08 »
Atoms and electrons jolly well do move at absolute zero. If they didn't it would be a breach of the uncertainty principle.
This movement is the zero point energy (about which an enormous amont of nonsense is talked).

If they're at absolute zero, they cannot be moving. I thought that is where the Uncertainty Principle comes in to prevent absolute zero being acheived.

By saying "zero point energy" you are implying a temperature above absolute zero. Any energy implies a temperature. Doesn't it?

#### lightarrow

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##### How fast do atoms travel?
« Reply #9 on: 23/12/2008 14:21:52 »

Interesting graphs. From it I see that the speeds corresponding to the maximums of the 4 curves are, rougly:

200 m/s
350 m/s
500 m/s
1100 m/s

Just for curiosity, I draw in a graph the four inverse squared speeds with respect to the 4 gas' masses (132; 40; 20; 4. m on x axis and 1/v2 on y axis): it's a quite perfect straight line (as it should be since kinetic energy is (1/2)mv2 and has the same value for all 4 gases: being monoatomic = just traslational kinetic energy).
Edit: clearly that works because those 4 curves are symmetrical enough to approximate the average speeds with the speeds of the maximums.
« Last Edit: 24/12/2008 11:08:07 by lightarrow »

#### Mr. Scientist

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##### How fast do atoms travel?
« Reply #10 on: 24/12/2008 02:15:50 »
Dear Naked Scientists,

At what speed, preferably in metres per second if applicable, does an atom travel from point a to point b and does this speed fluctuate or is it constant?

Warm Regards,

What do you think?

There are many atoms, which travel at different speeds. But there is a limit, which is lightspeed. For a single atom to travel faster than light, would mean that it would require more energy than the universe contained! So atoms move at difefrential speeds, but must move slower than c.

#### lightarrow

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##### How fast do atoms travel?
« Reply #11 on: 24/12/2008 11:17:18 »
There are many atoms, which travel at different speeds. But there is a limit, which is lightspeed. For a single atom to travel faster than light, would mean that it would require more energy than the universe contained! So atoms move at difefrential speeds, but must move slower than c.
Sorry if I correct you a little: no body/object can accelerate to faster than light speed, even with infinite energy. Actually the energy should be imaginary.

#### Mr. Scientist

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##### How fast do atoms travel?
« Reply #12 on: 24/12/2008 18:43:23 »
There are many atoms, which travel at different speeds. But there is a limit, which is lightspeed. For a single atom to travel faster than light, would mean that it would require more energy than the universe contained! So atoms move at difefrential speeds, but must move slower than c.
Sorry if I correct you a little: no body/object can accelerate to faster than light speed, even with infinite energy. Actually the energy should be imaginary.

I don't know why you are referring to superluminal speeds here, as in, imaginary tachyon matter, with a negative energy density, however, i was saying that rest mass has a limit under invariance with the speed of light.

Therego, i have no idea what you are talking about.

#### lightarrow

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##### How fast do atoms travel?
« Reply #13 on: 24/12/2008 20:31:38 »
There are many atoms, which travel at different speeds. But there is a limit, which is lightspeed. For a single atom to travel faster than light, would mean that it would require more energy than the universe contained! So atoms move at difefrential speeds, but must move slower than c.
Sorry if I correct you a little: no body/object can accelerate to faster than light speed, even with infinite energy. Actually the energy should be imaginary.

I don't know why you are referring to superluminal speeds here, as in, imaginary tachyon matter, with a negative energy density, however, i was saying that rest mass has a limit under invariance with the speed of light.

Therego, i have no idea what you are talking about.
Sorry, but I don't have idea what you are talking about too; you wrote:

"For a single atom to travel faster than light"

What did you mean?

#### Mr. Scientist

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##### How fast do atoms travel?
« Reply #14 on: 24/12/2008 20:47:58 »
There are many atoms, which travel at different speeds. But there is a limit, which is lightspeed. For a single atom to travel faster than light, would mean that it would require more energy than the universe contained! So atoms move at difefrential speeds, but must move slower than c.
Sorry if I correct you a little: no body/object can accelerate to faster than light speed, even with infinite energy. Actually the energy should be imaginary.

I don't know why you are referring to superluminal speeds here, as in, imaginary tachyon matter, with a negative energy density, however, i was saying that rest mass has a limit under invariance with the speed of light.

Therego, i have no idea what you are talking about.
Sorry, but I don't have idea what you are talking about too; you wrote:

"For a single atom to travel faster than light"

What did you mean?

Exactly what it said. Let me rephrase it;

For an atom, to travel faster than light, if it where possible, it would require an infinite amount of energy, more energy than the universe could maintain. IT WOULD BE A VIOLATION.

This is why an atom (which all atoms on the standard interpretation have\$ mass), must move at  speed lower than tht of c.

#### yor_on

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##### How fast do atoms travel?
« Reply #15 on: 25/12/2008 10:16:55 »
And what is those quarks and gluon's really?
So small but spanning such a wide area.

How dare they take so much space?
Does this mean that I'm mostly hot air?
Ah sorry, space?
But hot:)
« Last Edit: 25/12/2008 10:18:27 by yor_on »

#### DoctorBeaver

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##### How fast do atoms travel?
« Reply #16 on: 25/12/2008 10:27:45 »

Does this mean that I'm mostly hot air?
Ah sorry, space?
But hot:)

That depends how excited you are

#### lightarrow

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##### How fast do atoms travel?
« Reply #17 on: 25/12/2008 18:12:30 »
"For a single atom to travel faster than light"
What did you mean?

Exactly what it said. Let me rephrase it;
For an atom, to travel faster than light, if it where possible, it would require an infinite amount of energy, more energy than the universe could maintain. IT WOULD BE A VIOLATION.
It would require infinite energy to *reach* light speed. To overtake it, infinite energy wouldn't be enough, do you agree with it?

#### The Naked Scientists Forum

##### How fast do atoms travel?
« Reply #17 on: 25/12/2008 18:12:30 »