<h2>If you don't like math: A fraction of a second.</h2>
<h3>For math lovers:</h3>
<p>One proton is <span class="math-container">$8.414 \cdot 10^{-16}$</span> meters wide, and one Planck time is <span class="math-container">$5.391247 \cdot 10^{-44}$</span> seconds. This means that we are traveling at <span class="math-container">$\dfrac{8.414 \cdot 10^{28}}{5.391247} = 1.5606779 \cdot 10^{28}$</span> meters per second. Dividing by <span class="math-container">$299792458$</span> m/s, or <span class="math-container">$c$</span>, we get <span class="math-container">$5.205861 \cdot 10^{19}c$</span>. The observable universe is 93 billion light years in size, so it would take <span class="math-container">$\dfrac{93 \cdot 10^9 \cdot 86400 \cdot 365c}{5.205861 \cdot 10^{19}c} \approx 0.0564$</span> seconds to traverse the observable universe. This obviously is impossible, as faster-than-light travel <s>(username checks out)</s> violates the rules of general relativity (as we know it).</p>

CC BY-SA 4.0
2021-05-19T10:32:07.913Z
Strictly speaking, the problem isn't just general relativity but also special relativity. Going FTL means that there are inertial observers that see your trip take different time, including zero or a negative number of seconds. So the impossibility is not just that moving that fast as a material object isn't possible according to our current understanding of physics, but that the answer itself is somewhat undefined.
Anders Sandberg
CC BY-SA 4.0
2021-05-19T00:44:24.210Z
2021-05-19T00:44:24.210Z
WarpPrime
<p>If I could travel a super small distance (proton) in an even smaller time (Planck time), how long would it take me to cross the observable universe?</p>

<universe><light><speed>
Traversing a proton within the Planck time
TryingMyBest
# Traversing a proton within the Planck time

(Asked by: username_0 on 2021-05-18)

If I could travel a super small distance (proton) in an even smaller time (Planck time), how long would it take me to cross the observable universe?

**Tags:** universe, light, speed


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## 1 answers

### Answer by username_1 on 2021-05-19. Score: 6 | Accepted answer

## If you don't like math: A fraction of a second.

### For math lovers:

One proton is $8.414 \cdot 10^{-16}$ meters wide, and one Planck time is $5.391247 \cdot 10^{-44}$ seconds. This means that we are traveling at $\dfrac{8.414 \cdot 10^{28}}{5.391247} = 1.5606779 \cdot 10^{28}$ meters per second. Dividing by $299792458$ m/s, or $c$, we get $5.205861 \cdot 10^{19}c$. The observable universe is 93 billion light years in size, so it would take $\dfrac{93 \cdot 10^9 \cdot 86400 \cdot 365c}{5.205861 \cdot 10^{19}c} \approx 0.0564$ seconds to traverse the observable universe. This obviously is impossible, as faster-than-light travel ~~(username checks out)~~ violates the rules of general relativity (as we know it).

> **Comments:**
> **username_2**: Strictly speaking, the problem isn't just general relativity but also special relativity. Going FTL means that there are inertial observers that see your trip take different time, including zero or a negative number of seconds. So the impossibility is not just that moving that fast as a material object isn't possible according to our current understanding of physics, but that the answer itself is somewhat undefined.  

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