# Time dilation and blue-shifting **URL:** \ **Category:** Factual Questions\ **Created:** [April 17, 2025, 3:19am UTC](https://boards.straightdope.com/t/time-dilation-and-blue-shifting/1017123 "2025-04-17T03:19:37Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 19, 2025, 1:17pm UTC](https://boards.straightdope.com/t/time-dilation-and-blue-shifting/1017123/21 "2025-04-19T13:17:37Z")
Ah, true, you can have an object exceeding the speed of light in some medium, and that does result in an effect analogous to a boat wake or a sonic boom, from “photons piling up on each other”. ---
**Author:** ![74westy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/74westy/32/3950_2.png) [@74westy](https://boards.straightdope.com/u/74westy)\ **Post date:** [April 19, 2025, 1:24pm UTC](https://boards.straightdope.com/t/time-dilation-and-blue-shifting/1017123/22 "2025-04-19T13:24:27Z")
> [@Chronos](#): > > There’s a broad category of questions, asked in places like this, that amount to “What if this thing that violates the laws of physics were to happen. Wouldn’t that violate the laws of physics?”. I like the ones that ask, “If this thing violated the laws of physics, what do the laws of physics say would happen?” ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [April 19, 2025, 3:17pm UTC](https://boards.straightdope.com/t/time-dilation-and-blue-shifting/1017123/23 "2025-04-19T15:17:17Z")
> [@74westy](#): > > I like the ones that ask, “If this thing violated the laws of physics, what do the laws of physics say would happen?” That’s what I was trying to answer with my post about turning into pumpkins. There’s just no good answer, so magical things happen. Or not. And I don’t think @Kedikat was thinking of Cherenkov radiation. ---
**Author:** ![Kedikat](https://avatars.discourse-cdn.com/v4/letter/k/ed655f/32.png) [@Kedikat](https://boards.straightdope.com/u/Kedikat)\ **Post date:** [April 19, 2025, 3:40pm UTC](https://boards.straightdope.com/t/time-dilation-and-blue-shifting/1017123/24 "2025-04-19T15:40:39Z")
I wasn’t. I was wondering if such an effect would happen, that is why it can’t happen. Why an object can’t travel faster than light. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 19, 2025, 3:56pm UTC](https://boards.straightdope.com/t/time-dilation-and-blue-shifting/1017123/25 "2025-04-19T15:56:33Z")
I’m not sure how meaningful it is to point to one of the specific counterfactual results of a counterfactual situation, and say that that’s the specific reason it doesn’t happen. There are lots of other unphysical things that come up if you try to follow that chain of reasoning, and any of them can be pointed at as “the reason”. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [April 19, 2025, 4:08pm UTC](https://boards.straightdope.com/t/time-dilation-and-blue-shifting/1017123/26 "2025-04-19T16:08:01Z")
The stuff that goes at the speed of light is massless particles. Photons have momentum, but zero mass. Nothing can go _faster_ than the speed of light because that is geometrically impossible (to understand this you have to let go of the Newtonian view of the universe; it does not work like that). [Previous page](https://boards.straightdope.com/t/time-dilation-and-blue-shifting/1017123.md?page=1)