Is the speed of light really changing over time?

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In summary, the conversation discusses the biology professor's claim that the speed of light is no longer considered a constant. The professor mentions that scientists have stopped a beam of light using magnetic fields and that the speed of light is changing over time. However, there is no evidence to support these claims and they are not widely accepted in the scientific community. The conversation also touches on the professor's misinterpretation of the concept of the speed of light being a constant and the need for him to stick to his field of knowledge. The conversation concludes with a reference to a paper discussing the possibility of light being slowed down, but this is still a hypothesis and should not be treated as fact.
  • #1
kuahji
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My biology professor keeps talking about how the speed of light is no longer considered a constant. Anyway, he went on to quote how scientists have stopped a beam of light using magnetic fields. I've read a few popular science articles in the magazine New Scientists but found nothing that would indicate a violation of relativity or even one using magnetic fields. He also stated that the speed of light is changing over time. He used an example regarding how the sun will eventually run out of energy & between that time the speed of light will slow down as a result.

So...
Can anyone point me in the right direction of information on the stopping light with magnetic fields? (if there really were/are any)

Does anyone know of any articles regarding the slowing of the speed of light?

Overall, I understand a biology professor is not a physics professor but he keeps using various examples as if they were facts. Often stating "we once though the speed of light was a constant."
 
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  • #2
When we refer to the speed of light being a constant, we're usually referring to the speed of light in a vacuum. Any slowing of the speed of light involves its transmission through a medium of some sort. For example, the speed of light in water is about 3/4 the speed of light in vacuum. This is the basis of refraction in lenses etc.

I understand there are theories which incorporate or predict a variable speed of light (in vacuum), but as far as I know they are speculative, and not widely accepted.
 
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  • #3
kuahji said:
My biology professor keeps talking about how the speed of light is no longer considered a constant. Anyway, he went on to quote how scientists have stopped a beam of light using magnetic fields.

i'd like to see the peer-reviewed article for that one. I highly doubt its as he represented it.

I've read a few popular science articles in the magazine New Scientists but found nothing that would indicate a violation of relativity or even one using magnetic fields. He also stated that the speed of light is changing over time. He used an example regarding how the sun will eventually run out of energy & between that time the speed of light will slow down as a result.

He said what? Slow down as a result of what? The sun running out of hydrogen fuel?



So...
Can anyone point me in the right direction of information on the stopping light with magnetic fields? (if there really were/are any)

Does anyone know of any articles regarding the slowing of the speed of light?

Overall, I understand a biology professor is not a physics professor but he keeps using various examples as if they were facts. Often stating "we once though the speed of light was a constant."


I'm pretty sure he's mistating and misquoting whatever he's read (probably not intentionally).

What jtbell said pretty much covers it.
 
  • #4
"a biology professor is not a physics professor."
 
  • #5
This is a nice paper on "slowing light down": http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000095000025253601000001&idtype=cvips&gifs=yes [Broken]
 
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  • #6
kuahji said:
Overall, I understand a biology professor is not a physics professor but he keeps using various examples as if they were facts. Often stating "we once though the speed of light was a constant."

The speed of light in vacuum is constant!
Your biology professor should stick to his field of knowledge.
 
  • #7
EL said:
The speed of light in vacuum is constant!
Your biology professor should stick to his field of knowledge.


The professor is perhaps referring to hypotheses that c may have varied over the course of the universe. He should not be treating these mere hypotheses ("theories in search of confirmation") as facts or draw social conclusions from them.
 

What is the speed of light?

The speed of light is a fundamental constant in physics, denoted by the symbol c. In a vacuum, it is approximately 299,792,458 meters per second.

What is the theory of relativity?

The theory of relativity is a fundamental theory in physics developed by Albert Einstein, which describes the relationships between space, time, and gravity. It consists of two main theories: the special theory of relativity and the general theory of relativity.

What is the difference between special and general relativity?

The special theory of relativity deals with the laws of physics in inertial (non-accelerating) reference frames, while the general theory of relativity extends these laws to non-inertial (accelerating) reference frames by incorporating the effects of gravity.

How does the theory of relativity impact our understanding of the universe?

The theory of relativity has revolutionized our understanding of the universe by providing a deeper understanding of the relationships between space, time, and gravity. It has also been crucial in the development of technologies such as GPS and in the study of black holes and the origin of the universe.

What is time dilation and how does it relate to the theory of relativity?

Time dilation is a phenomenon predicted by the theory of relativity, where time appears to pass slower for objects that are moving at high speeds or experiencing strong gravitational forces. This concept has been confirmed through experiments and is essential in understanding the behavior of particles traveling at near-light speeds.

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