What Is the Lightest Weight Measurable by a Sensitive Scales?

[scupydog]

Scupydog is my dad i would like to ask a question that my dad thinks he can answer.

If you had a very sensitive weighing scales and you put the lightest thing on them, what would it weigh.

Daisy 11.

 

[Werg22]

Everything that is matter has mass. A bread crumb has a weight.

 

[scupydog]

Everything that is matter has mass. A bread crumb has a weight.

What would have the smallest mass.

 

[Werg22]

To my knowledge, an elementary particle called the neutrino has the smallest mass. I could be wrong, however.

 

[disregardthat]

The smallest mass that can exist in nature is 2.176 × 10-8 kg which is the Planck mass. I don't know what has that mass though..

 

[billiards]

Weight is a force, it depends on the mass of thing you're weighing and the acceleration due to gravity where you are. weight=mass*gravity

Basically you weigh more when gravity is stronger, gravity is about the same everywhere on the surface of the Earth, but actually it's slightly stronger at the poles - if you went to the North Pole you'd weigh more than if you were on the equator!

 

[disregardthat]

He meant mass, so weight doesn't have much to do with this.

Either way you see it, the lightest thing would be the thing with the smallest mass, if you compare it to something with the same gravitational force on it...

 

[scupydog]

The smallest mass that can exist in nature is 2.176 × 10-8 kg which is the Planck mass. I don't know what has that mass though..

My dad said the same thing.

 

[disregardthat]

Yes I did, son.


:P

 

[ranger]

Yes I did, son.


:P

Daisy is an odd name for a son :)

 

[disregardthat]

Oh, it's a girl. Oh well, my lie has been revealed.

 

[scott1]

To my knowledge, an elementary particle called the neutrino has the smallest mass. I could be wrong, however.

I don't that what she's asking. That would the wo..universe's lightest object but not the smallest mass possible. I don't know if there's a limit to how small things could get.

 

[disregardthat]

Yes there is, and it is restricted to the Planck length as far as I know. The smallest 'amount' of mass that can be set in the smallest possible volume (planckmeter^3) is excactly the Planckmass.

If you are talking about weight, the smallest theoretical possible weight is 0, if not other mass is affecting the object, or is affecting it equally on all sides.
But weight is not the question here, because it differs.

 

[neutrino]

My dad said the same thing.

The electron, which is certainly NOT the lightest particle of matter in the universe, is nearly a million million millon million times lighter than anything that might have Planck mass.

This may give you some idea: http://en.wikipedia.org/wiki/Orders_of_magnitude_(mass)

To my knowledge, an elementary particle called the neutrino has the smallest mass. I could be wrong, however.

The last time I stood on a weighing scale, it showed a little more than a few eV.

 

[Gokul43201]

The smallest mass that can exist in nature is 2.176 × 10-8 kg which is the Planck mass.

How is it then, that this is roughly the mass of one of my hairs? I can name a lot of things that are lighter than this.

My dad said the same thing.

Even dads can be wrong every once in a while. Most of the time, they're right though!

 

[Werg22]

How is it then, that this is roughly the mass of one of my hairs? I can name a lot of things that are lighter than this.


Even dads can be wrong every once in a while. Most of the time, they're right though!

Haha, there was a time were I took my dad for a textbook. The innocence of childhood...

 

[disregardthat]

How is it then, that this is roughly the mass of one of my hairs? I can name a lot of things that are lighter than this.

You tell me!

I thought the Planck units were the smallest units you could use, and that exists...

 

[Doc Al]

Why don't you look up what Planck mass means and how it is defined?

 

[disregardthat]

I did, I read an article about it... I'll look up on it again...

 

[hustleberry]

no offense but this question has no meaning of course it would find the wieght if it was SENSITIVE ENOUGH! if not it would'nt register anythinf

 

[Ki Man]

you'd probably need a cyclotron or something in that high-energy category to even detect its presence, let alone measure it

 

[disregardthat]

Well, the weight was supposed to measure it's WEIGHT, not it's amount of energy, right?

I read about Plancks constant, didn't udnerstand a thing, wikipedia is so unclear on definitions.

What IS the smallest weight then?

 

[neutrino]

What IS the smallest weight then?

There is none, AFAIK. There might be a particle* which has the smallest measured mass (let's avoid weight), but if you're looking for an absolute lower limit (greater than 0) set by nature, I don't think there is one. Someone correct me if I'm wrong.

*most probably a neutrino, as of now

 

[disregardthat]

I really was convinced that this lower limit was the Planck mass.

I find it hard to believe that you could cut material in half endlessly and never get to the point where you can't cut no more.

 

[cristo]

I read about Plancks constant, didn't udnerstand a thing, wikipedia is so unclear on definitions.

Here is the wiki article on the Planck Mass: http://en.wikipedia.org/wiki/Planck_mass.

I think the definition here is quite clear.

 

[billiards]

You can't actually weigh a photon but I suppose they have as small a mass as is conceivable - zero.

 

[scupydog]

Here is the wiki article on the Planck Mass: http://en.wikipedia.org/wiki/Planck_mass.

I think the definition here is quite clear.

if i get three pieces of string of Planck length and form them into a circle then the diameter is less than the Planck length

 

[cristo]

if i get three pieces of string of Planck length and form them into a circle then the diameter is less than the Planck length

What do you intend to make these pieces of string out of? The Planck length is of the order 10^-35m, whereas the radius of an atom is of the order 10^-13m.

 

[scupydog]

Here is the wiki article on the Planck Mass: http://en.wikipedia.org/wiki/Planck_mass.

I think the definition here is quite clear.

What do you intend to make these pieces of string out of? The Planck length is of the order 10^-35m, whereas the radius of an atom is of the order 10^-13m.

so the Planck length has to be a circumferance because it can't be a radius or must it be a radius

 

[vivesdn]

As for the wiki article mentioned, I would not say that the Planck mass is the smallest mass possible. It is the mass of a particular type of black hole whose radius is 'roughly' the Planck length. It might result that it is the densest mass possible (just a wild guess).

 

[cristo]

so the Planck length has to be a circumferance because it can't be a radius or must it be a radius

Well, neither. The Planck length is thought to be the smallest distance that can exist and still have meaning. Of course, this is a theory, and so has never been tested, but no smaller unit of length has been measured yet.

The point I was attempting to make is that we can't make a piece of string of length equal to Planck's length out of everyday, physical substances, and thus your idea of putting three pieces of string together to form a circle, with diameter less than the Planck length cannot be done.

I hope this makes sense, however I am no expert in this field. If anyone more qualified is reading this and can explain, please jump in!

 

[disregardthat]

:D I got it!

Since no one is, I will jump to the conclusion, the Planck length IS the smallest length measurable and that makes sense in the univers. The Planck mass is the LARGEST amount of mass that can be filled in this volume.

So, any expert, tell me if I got it totally wrong and need to read about Planck constants, or if i may have something right here.

 

[neutrino]

I'm no expert, but I found these sites informative.

http://math.ucr.edu/home/baez/lengths.html#planck_length
http://www.phys.unsw.edu.au/einsteinlight/jw/module6_Planck.htm

 

[vivesdn]

So the Planck mass in a volume of the Planck length needs relativity, gravity and quantum mechanics to describe its state. So the slightest mass possible remains unknown. Is a neutrino heavier than a photon (as far as I remember, a photon is said to have null mass at rest, but it moves at c, and then its mass is not null)?

 

[ranger]

So the slightest mass possible remains unknown. Is a neutrino heavier than a photon (as far as I remember, a photon is said to have null mass at rest, but it moves at c, and then its mass is not null)?

Regardless of velocity, a photon will have zero mass.

m_r = \frac{m_0}{\sqrt{1 - v^2/c^2}}

m_r is the relativistic mass, which increases with velocity [this is what your trying to say increases]. Now if m_0 is the rest mass, which is zero for a photon, the quotient would be zero. Therefore the relative mass of a photon is also zero and does not increase with velocity.

 

[Gokul43201]

Regardless of velocity, a photon will have zero mass.

m_r = \frac{m_0}{\sqrt{1 - v^2/c^2}}

m_r is the relativistic mass, which increases with velocity [this is what your trying to say increases]. Now if m_0 is the rest mass, which is zero for a photon, the quotient would be zero. Therefore the relative mass of a photon is also zero and does not increase with velocity.

But if v=c, which it is, for a photon, then the denominator is also zero! So m_r need not be zero.

 

[Hootenanny]

As I have many times before, I believe the discussion of any mass other than invariant mass is meaningless; it only works to add confusion to any matter in which it is discussed. It is not the 'mass' of a particle which actually increases (i.e. it doesn't get more massive) it is simply the momentum of the particle which increases faster than classically predicted.

 

[disregardthat]

So you mean that p=ma is not correct?
Momentum=mass*velocity

At large scales that is. So when the velocity is rising, the momentum is too, when the mass stays the same, but when you say the momentum is rising because of the high speeds comparable to light do you mean as another factour outside this equation, and not just velocity's effect on momentum?
Becasue if velocity rises, momentum does too, that is clear, but when velocity is c, the momentum is in relativity infinite, so that equation must be wrong.

 

[marlon]

Regardless of velocity, a photon will have zero mass.

m_r = \frac{m_0}{\sqrt{1 - v^2/c^2}}

m_r is the relativistic mass, which increases with velocity [this is what your trying to say increases]. Now if m_0 is the rest mass, which is zero for a photon, the quotient would be zero. Therefore the relative mass of a photon is also zero and does not increase with velocity.

No, that's an incorrect conclusion. We need to v=c for the photon case and you will see that relativistic mass has no physical meaning in the case of a photon.

It is not the 'mass' of a particle which actually increases (i.e. it doesn't get more massive) it is simply the momentum of the particle which increases faster than classically predicted.

Exactly

marlon

 

[ranger]

Hi marlon, I'm kind of confused now. With regards to Hootenanny's reply which you quoted; strictly speaking of Momentum=mass*velocity or p = \frac{m_0v} {\sqrt{1 - v^2/c^2}} won't the momentum be zero in both cases? Unless for situations like this, momentum is somehow found by inclusion of the wavelength as the particle has zero mass?

Edit: aw crap, looks like my latex formatting for relativistic momentum is messed up.

 

[Hootenanny]

Unless for situations like this, momentum is somehow found by inclusion of the wavelength as the particle has zero mass?

Exactly! The momentum of a photon is defined as p = h/\lambda and can be derived from general energy expression E = \sqrt{(pc)^2 +(mc^2)^2}.

 

[marlon]

Hi marlon, I'm kind of confused now. With regards to Hootenanny's reply which you quoted; strictly speaking of Momentum=mass*velocity or p = \frac{m_0v} {\sqrt{1 - v^2/c^2}} won't the momentum be zero in both cases?

Not in the case of a photon because you get 0/0, this formula does not apply to photons !

Unless for situations like this, momentum is somehow found by inclusion of the wavelength as the particle has zero mass?

Edit: aw crap, looks like my latex formatting for relativistic momentum is messed up.

Correctly. Hootenanny answered this question perfectly so i can only quote it to be clear :

Exactly! The momentum of a photon is defined as p = h/\lambda and can be derived from general energy expression E = \sqrt{(pc)^2 +(mc^2)^2}.

marlon

 

[vivesdn]

As I have many times before, I believe the discussion of any mass other than invariant mass is meaningless; it only works to add confusion to any matter in which it is discussed. It is not the 'mass' of a particle which actually increases (i.e. it doesn't get more massive) it is simply the momentum of the particle which increases faster than classically predicted.

I've recently read an article that states exactly the opposite. Energy and mass are the same thing, just related by a factor (c^2).
According to this view, the relation of kynetic energy to total energy is a value between 0 an 1, given by 1-(1-v^2/c^2)^1/2. So, if you move at c, all your energy is kynetic energy. So mass at rest has no meaning for a photon as you'll never see a photon not moving at c.