Does Zero Rest Mass Mean No Particle Exists?

[Tio Barnabe]

If we equate Planck expression $E = h \nu$ with Einstein's $E = m_o c^2$ we get

$$m_o c^2 = h \nu$$ what can we conclude from this? Since the frequency $\nu$ above is directly related to the frequency of which a particle will be found at a given point, would the above expr mean that if the rest mass $m_o = 0$ then we will never find the particle?

 

[Nugatory]

would the above expr mean that if the rest mass $m_o = 0$ then we will never find the particle?

No, because $E=m_0c^2$ does not apply to particles with zero rest mass. That equation is the $p=0$ special case of $E^2=(m_0c^2)^2+(pc)^2$. However, a particle with zero rest mass is always moving, so $p$ is always non-zero and the special case doesn't apply.

 

[Tio Barnabe]

No, because $E=m_0c^2$ does not apply to particles with zero rest mass. That equation is the $p=0$ special case of $E^2=(m_0c^2)^2+(pc)^2$. However, a particle with zero rest mass is always moving, so $p$ is always non-zero and the special case doesn't apply.

Then maybe dr. Roger Penrose made a mistake in the interview below?

 

[Vanadium 50]

what can we conclude from this?

Nothing.

 

[haushofer]

Then maybe dr. Roger Penrose made a mistake in the interview below?

It seems to me a very vague reasoning, yes (around 8 minutes; please point this out the next time you refer to part of a video). He first argues that in the early universe, due to the high temperatures we can neglect the mass of particles and treat them as effectively massless. Then he argues that via Planck's relation this means that time looses its meaning, because clocks are massive.

I don't get that kind of reasoning.

 

[PeterDonis]

Then maybe dr. Roger Penrose made a mistake in the interview below?

He's talking about a speculation that has been proposed to "answer" the question of how the universe began (by basically arguing that the concept of "began" isn't meaningful in the very early universe). It doesn't contradict what @Nugatory said, because Penrose is not arguing that the equation $E = m_0 c^2$ should apply to particles with zero rest mass. In terms of your OP, his argument would basically be that the equation $E = h \nu$ stops applying in the very early universe, because $\nu$ is no longer well-defined (since time is no longer well-defined).

 

[Mister T]

Then maybe dr. Roger Penrose made a mistake in the interview below?

Nowhere in that discussion did he equate the mass of a photon to $h \nu$. The mass of a photon is always zero, however the mass of a collection of photons does not have to be zero. Can you be more specific about what it was he said? The video is 17 minutes long.
.

 

[Mister T]

He's talking about a speculation that has been proposed to "answer" the question of how the universe began (by basically arguing that the concept of "began" isn't meaningful in the very early universe).

Thank you. Somehow I always get the impression from Penrose that he has not expended any effort towards making his explanations clear.