Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Alex Havers on 13/10/2008 22:10:32
-
Alex Havers asked the Naked Scientists:
Hi there.. A quick question from beautiful Vancouver!
What particles make gravity and are they able to move as fast as light?
Thanks, I'll look forward to your response - I listen avidly every week (http://www.thenakedscientists.com/HTML/podcasts/) with my science class!
What do you think?
-
The simple answer is any particles that have mass create a gravitational field and no they cannot travel at light speed precisely because they have mass. However if you mean the hypothetical particles that mediate the gravitational force between massive particles the answer is "gravitons" the gravitational equivalent of photons for the electromagnetic interactions and yes they do travel at light speed just like photons but most gravitational interactions are so slow that the graviton energies are almost vanishingly small and it is unlikely that individual graviton based events will ever be detected.
-
It is tempting to compare Gravitons to Neutrinos which too were once considered to be massless although it is now known that they possess a small mass and come in three 'flavours'.
this provides one explanation as to the impossibility of a gravitational shield as the Neutrino requires light years of lead to shield them how much more so the vastly less energetic Graviton.
The limiting velocity is an interesting problem although measurements have been made it is so close to c that it is not really possible to tell if the difference is zero or not.
Has the velocity of the Neutrino been determined ?, is there an limit as to how low the mass of a particle must be for it to travel at c or is it truly zero?.
-
Particles with high energies with respect to their rest mass travel arbitrarily close to the velocity of light but still slightly less than light this means that at high energies accelerators are just adding energy to the particle and not making them go significantly faster they just have more momentum and are more difficult to persuade to change their direction.
This fact is used in the large hadron collider and makes the design a bit simpler.
It is also interesting to consider how this affects what was going on in the early stages of the big bang when all the particles had many millions of times their rest mass of energy, everything was all going at about the same speed ie the velocity of light.
This produces some even more interesting effects when you consider what happens to particles inside a rotating black hole where the particles would all be travelling in their orbits at (very very close to) the velocity of light but would be gradually slowing down with respect to each other as the orbits settle down and the "temperature" gradually cools.
-
Is it possible as it is postulated that both time and distance are quantized with a minimum value for each that the same applies to velocity so that a sufficiently energetic light mass particle such as a Neutrino or Graviton can actually travel at c