# The Naked Scientists Forum

### Author Topic: Are electrons affected by gravity?  (Read 24026 times)

#### thebrain13

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##### Are electrons affected by gravity?
« on: 01/11/2007 01:50:03 »
how do we know that gravity affects electrons? We cant build anything exclusively out of electrons, and if we do isolate them, we have to keep them there using something made partly from protons.(right?) Can we actually ever get electrons by themselves? how do we know that gravity doesnt just affect positive mass, and the much larger positive mass is just dragging the much smaller negative mass along?
« Last Edit: 10/10/2015 12:57:25 by chris »

#### DoctorBeaver

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##### gravity and electrons
« Reply #1 on: 01/11/2007 14:08:29 »
Electrons have such little mass that gravity has a negligible effect on them. To put it in perspective, in a hydrogen atom the gravitational force between the electron and the proton is approximately 10-43 times smaller than the electrical force.

#### lyner

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##### gravity and electrons
« Reply #2 on: 01/11/2007 14:26:51 »
Quote
Electrons have such little mass that gravity has a negligible effect on them
It's more a matter of e/m than just m. (The ratio of charge to mass).
It's interesting to calculate the electric force between two standard units of charge (coulomb) separated by the standard unit of length (metre), then to do the same thing, working out the gravitational force  between two masses (kg ) separated by one metre.
One so huge and one so small.

I notice , brain13,  you are talking of positive and negative masses - both have positive mass - it's the charges that have different signs.

But electrons certainly do exhibit and possess momentum - therefore, because they are not traveling at c, they must have mass. So, unless there is something wierd about them, they will have weight, too.

#### thebrain13

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##### gravity and electrons
« Reply #3 on: 01/11/2007 15:54:28 »
I didnt mean to say that electrons have mass that is less than zero, or negative mass, as your thinking of it. I meant the mass it does have is negatively charged, and was wondering how do we know that negatively charged mass is affected by gravity the same way that positively charged mass is.

#### Mr Andrew

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##### gravity and electrons
« Reply #4 on: 01/11/2007 22:46:53 »
Charge and mass are totally seperate.  Gravity only affects mass...Electricity only affects charge.

#### thebrain13

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##### gravity and electrons
« Reply #5 on: 01/11/2007 23:26:07 »
Right, Im asking, how do we know that.

#### thebrain13

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##### gravity and electrons
« Reply #6 on: 05/11/2007 22:37:15 »
In other words im asking, what experiment shows that gravity affects electrons?

Not what theory says gravity affects electrons.

#### Mr Andrew

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##### gravity and electrons
« Reply #7 on: 06/11/2007 02:09:30 »
If electrons weren't affected by gravity then a cathode ray would be bent due to the earth spinning and moving through space all of that (Newton's First Law).  It isn't.

#### thebrain13

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##### gravity and electrons
« Reply #8 on: 06/11/2007 02:49:37 »
As short as that explanation is, I dont understand what you are trying to say.

#### JP

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##### gravity and electrons
« Reply #9 on: 06/11/2007 18:09:48 »
how do we know that gravity doesnt just affect positive mass, and the much larger positive mass is just dragging the much smaller negative mass along?

I'm interpreting you as meaning "What if gravity only affects protons and neutrons, and this accounts for the gravitational mass of matter?"

I don't think there is an experiment that shows electrons are affected by gravity.  As DoctorBeaver said, electrons have such a small mass, and electromagnetic forces are so large compared to gravity, that gravity gets swamped out by electromagnetism when looking at electrons.  However, we do know that electrons have inertial mass (the mass that requires you to put in energy in order to accelerate them), as sophiecentaur mentioned.  It's generally accepted that inertial mass and gravitational mass are equivalent, though actually demonstrating this experimentally at the quantum level is difficult (again, due to gravity being so tiny compared to other quantum-level forces).  More importantly, there's no good reason to assume that electrons aren't affected by gravity: everything we're able to measure is affected by gravity regardless of its charge, so why should it be different for electrons?

#### Soul Surfer

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##### gravity and electrons
« Reply #10 on: 06/11/2007 18:13:37 »
Mr Andrew that looks like a load of tripe.

It is quite easy in theory to show that electrons respond to gravity.

Electrons like everything else will fall with the acceleration of gravity like a shot from a gun so if you shoot a beam horizontally so if you set up a fine beam of electrons running a long distace horizontally through a small hole and then turn the electron beam apparatus upside down the electrons will miss the hole because the gravity causes the beam to bend in the other direction.  Any residual electric or magnetic field effects will be identical only the gravitiatinal effect will change.

In practice this experiment is quite difficult to carry out and I'm not sure if it has actually been done. but gravitational effects on subatomic particles have to be allowed for in certain critical precise experimentation
« Last Edit: 06/11/2007 18:17:11 by Soul Surfer »

#### syhprum

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##### gravity and electrons
« Reply #11 on: 06/11/2007 19:54:53 »
I can not remember the exact details but there was a famous experiment to determine the e/m ratio where charged tiny oil drops were observed falling and the amount of charge varied until the lowest rate of fall was observed

Sorry muddled thinking !

It is generally agreed that the electron has a mass of 1/1836 that of the proton and like all objects with mass is subject to gravitational attraction

#### JP

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##### gravity and electrons
« Reply #12 on: 06/11/2007 20:39:45 »
That's the experiment [Millikan's oil drop experiment] I thought of first, syphrum.  However, the gravitational force in this experiment is due to the mass of the entire oil drop, and the electron mass is a negligible contribution to it.

#### chrisdsn

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##### gravity and electrons
« Reply #13 on: 06/11/2007 23:23:55 »
You can work out the ratio of the mass of the electron to it's charge
by measuring the deflection of a beam of electrons in a magnetic field.

http://phoenix.phys.clemson.edu/labs/cupol/eoverm/index.html [nofollow]

The aforementioned Millikan's oil drop will tell you the charge
of an electron (kinda: it's very hard to do right; even Millikan
got it a little wrong). Combine the two and you get the mass.

#### syhprum

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##### gravity and electrons
« Reply #14 on: 07/11/2007 22:26:42 »
When an electron meets a positron and there is mutual annihilation with the emission of a .511 Mev gamma photon does this not give you the electrons mass by the familiar e=mc^2 formula.

#### lightarrow

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##### gravity and electrons
« Reply #15 on: 08/11/2007 13:32:08 »
how do we know that gravity affects electrons? We cant build anything exclusively out of electrons, and if we do isolate them, we have to keep them there using something made partly from protons.(right?) Can we actually ever get electrons by themselves? how do we know that gravity doesnt just affect positive mass, and the much larger positive mass is just dragging the much smaller negative mass along?
I've just turned of 90° the CRT Monitor of my computer: the image is slightly changed (luminosity and colours).
This means that gravity DO affect electrons!
Simple, isnt'it?

#### JP

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##### gravity and electrons
« Reply #16 on: 08/11/2007 16:20:38 »
how do we know that gravity affects electrons? We cant build anything exclusively out of electrons, and if we do isolate them, we have to keep them there using something made partly from protons.(right?) Can we actually ever get electrons by themselves? how do we know that gravity doesnt just affect positive mass, and the much larger positive mass is just dragging the much smaller negative mass along?
I've just turned of 90° the CRT Monitor of my computer: the image is slightly changed (luminosity and colours).
This means that gravity DO affect electrons!
Simple, isnt'it?

That's almost certainly due to the electron beam being affected by the Earth's magnetic field.  The magnetic field-electron interaction force should be much larger than the gravity-electron interaction.  If you could eliminate the magnetic effects, then this experiment would work, but given the tiny gravitational force, it's probably not a realizable experiment at the moment.

Everything being proposed here is good for determining the inertial mass of an electron, but I'm pretty convinced that we just don't have the technology to measure whether this is also gravitational mass: i.e. "does gravity affect electrons the same as larger objects?"  Of course, there's no good reason that I know of to assume that it doesn't, and plenty of good reasons to assume that it does.

#### syhprum

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##### gravity and electrons
« Reply #17 on: 08/11/2007 17:25:32 »
When matter orbits a black hole it is heated to such a degree that it is completely ionised, if the gravitational effect was different between Electron and Protons would this not show up in the spectrum of the electromagnetic radiation produced

#### lightarrow

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##### gravity and electrons
« Reply #18 on: 08/11/2007 18:13:14 »
how do we know that gravity affects electrons? We cant build anything exclusively out of electrons, and if we do isolate them, we have to keep them there using something made partly from protons.(right?) Can we actually ever get electrons by themselves? how do we know that gravity doesnt just affect positive mass, and the much larger positive mass is just dragging the much smaller negative mass along?
I've just turned of 90° the CRT Monitor of my computer: the image is slightly changed (luminosity and colours).
This means that gravity DO affect electrons!
Simple, isnt'it?

That's almost certainly due to the electron beam being affected by the Earth's magnetic field.  The magnetic field-electron interaction force should be much larger than the gravity-electron interaction.  If you could eliminate the magnetic effects, then this experiment would work, but given the tiny gravitational force, it's probably not a realizable experiment at the moment.

Everything being proposed here is good for determining the inertial mass of an electron, but I'm pretty convinced that we just don't have the technology to measure whether this is also gravitational mass: i.e. "does gravity affect electrons the same as larger objects?"  Of course, there's no good reason that I know of to assume that it doesn't, and plenty of good reasons to assume that it does.
Yes, you're right. My mistake.
« Last Edit: 08/11/2007 18:15:25 by lightarrow »

#### thebrain13

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##### gravity and electrons
« Reply #19 on: 08/11/2007 18:48:18 »
If you could show that electrons responded in the opposite way to gravity than protons do, that would be a big step in unifying gravity and electromagnetism. Dont ya think?

#### lyner

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##### gravity and electrons
« Reply #20 on: 08/11/2007 19:04:23 »
There are many occasions when a heavy negative ion will exhibit it mass / weight so what would be so special about negative charge in that case?
Even the drops in the Millican oil drop experiment can be negatively charged. They  don't  appear to behave differently. Why would you want them to?
Conversly, positrons (positive charged particles with the same mass as the electron) exist. They don't last long but would you expect them to behave differently to electrons as regards their mass. whilst they do exist?
'If' you could show an effect it would be good but, with all these  'it would be nice if' statements, you need experimental evidence to take it any further.
The problem is that electronic forces are so much stronger than gravitational ones.

#### syhprum

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##### gravity and electrons
« Reply #21 on: 08/11/2007 19:23:42 »
"positrons (positive charged particles with the same mass as the electron) exist. They don't last long"
Is there any reason to suppose that Positrons have any different life than Electrons?.
Of course when they come in contact with Electrons there is mutual annihilation but on those grounds we could say Electons have a short life!

#### thebrain13

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##### gravity and electrons
« Reply #22 on: 08/11/2007 19:43:45 »
Im not saying negatively charged ions fall up. I would predict the opposite. Because negative ions have protons in them, and the mass of the proton is way bigger than the electons, thus it should behave (almost) the same as if it was just a proton by itself.

#### Mr Andrew

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##### gravity and electrons
« Reply #23 on: 08/11/2007 23:00:08 »
I'm sorry, I mistyped...the cathode ray is bent, not straight, just like the path of a bullet is bent towards the earth (which is affected by gravity).  This would imply that electrons are affected by gravity also.  One experiment would be to take a negative ion and measure its momentum in a collision and, if you know its velocity, you can calculate its mass.  Comparing this mass to the mass derived from weight would tell you if there was an 'anti-gravity' acting on the electrons in the ion (if it was larger calculated with momentum than with weight then there must be some other force acting on it).  Was that clear?

#### lyner

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##### gravity and electrons
« Reply #24 on: 09/11/2007 00:00:01 »
Are you proposing that it is the negativity of the charge that makes it, somehow, different, gravitationally? What would be the effect on a positron, in a similar experiment? Why choose the negative charged particle (the chosen sign is totally arbitrary, remember) to be the one which would have a 'negative' gravitational influence?

#### The Naked Scientists Forum

##### gravity and electrons
« Reply #24 on: 09/11/2007 00:00:01 »