# Relativistic travel trades short trips for decades on Earth

Markdown copy of https://realalpha.app/s/relativistic-travel-trades-short-trips-for-decades-on-earth/ on Real Alpha, the best minutes from long interviews with the people building AI. Cite and link the page, not this copy.

- Speaker: [Kevin Knuth](https://realalpha.app/people/kevin-knuth/) · Kevin Knuth is a physics professor at the University at Albany. · Led a multimodal UAP study combining optical, infrared, weather-radar and radiation data.
- Host: [Brian Keating](https://realalpha.app/people/brian-keating/) · Host, Into the Impossible With Brian Keating
- Show: Into the Impossible With Brian Keating
- Episode: [Physics Professor: How Much Power Does a UFO Really Need?](https://realalpha.app/v/EKlLswUgyRI/), Nov 11, 2026
- Moment: 22:58 to 26:31 of the episode (4 min), playing on https://realalpha.app/s/relativistic-travel-trades-short-trips-for-decades-on-earth/; the episode from there: https://realalpha.app/v/EKlLswUgyRI/?t=1378

## Quote

> “For everybody in the galaxy, it takes 40 years. **For the traveler, it takes less than two days**.”
> — [Kevin Knuth](https://realalpha.app/people/kevin-knuth/) at [24:53](https://realalpha.app/v/EKlLswUgyRI/?t=1493) · Into the Impossible With Brian Keating

## Takeaways

1. At 1,000 Gs, the talk estimates reaching 90% of light speed in 17 hours.
2. A trip to nearby stars could take days for the travelers.
3. Relativity means decades could pass on Earth during that trip.

## About this segment

Kevin Knuth uses extreme acceleration to illustrate how relativistic travel could make distant stars reachable in a traveler’s lifetime. The catch is that far more time would pass for people back on Earth.

From “Physics Professor: How Much Power Does a UFO Really Need?”, Nov 11, 2026. [Watch the full episode](https://realalpha.app/v/EKlLswUgyRI/)

## Transcript

Transcribed by machine (Whisper) from the episode’s audio, so a word may be off here and there.

[23:06](https://realalpha.app/v/EKlLswUgyRI/?t=1386) What if this is actually a spacecraft? I mentioned here, you can get to the moon in 53 minutes. What if you were traveling further? And I make this point in the paper. Not only do these objects have flight characteristics necessary for interstellar travel, excuse me, they would make excellent interstellar craft. so a 1000 g acceleration, one-fifth of what the Nimitz case was observed doing, and one-tenth of the acceleration that was observed at JAL, you can get to 90% the speed of light in about 17 hours.

[23:39](https://realalpha.app/v/EKlLswUgyRI/?t=1419) Once you're going 90% the speed of light, relativity kicks in. Time slows down, distances change, you can actually travel much, much further. If these objects can sustain an acceleration in space, a 1000 g acceleration will get you to 30% the speed of light in 2.7 hours. How far could you go? Well, here's some examples. The Nimitz tic-tacs could get to the nearest star, Proxima Centauri, in less than one and a half days.

[24:10](https://realalpha.app/v/EKlLswUgyRI/?t=1450) It's a day trip. And actually could make it out to Zeta Reticuli in less than two days. you know this is the amount of time it'll take you to drive from new york to florida you could get to the nearest stars right within 40 light years and there's what there's probably 80 sun like stars in the 40 light year range i don't know the exact number way more than i think thousand i think i was just thinking about sun like stars you've got red red dwarves which are good trappist one is a red dwarf it goes around a red dwarf star so there's plenty of plenty of places to go yeah so these craft now now granted and you'll hear you'll hear scientists say this all the time when they complain about interstellar travel say oh and even if you can go fast it'll still take you you know 40 years to get to zeta reticuli well it'll take you 40 years in the

[25:00](https://realalpha.app/v/EKlLswUgyRI/?t=1500) Frame of the galaxy. For everybody in the galaxy, it takes 40 years. For the traveler, it takes less than two days. There's a time difference, and just because time slows down. Now, what that means is that you can't fly from Zeta Reticuli to the sun, hang out for an afternoon, and then fly back to Zeta Reticuli and make it home for dinner. For you, it'll be a four-day trip. For everybody on Zeta Reticuli or Earth, it'll be in 80 years.

[25:30](https://realalpha.app/v/EKlLswUgyRI/?t=1530) trip right so so this is what makes this is what makes interstellar travel hard not the fact that you can do it do you want to is the question and actually i gave a talk at scu one of the first scu meetings where i i noted that if you actually had a nomadic society so that you had a society that lived on their spaceships didn't live on a planet they lived on spaceships they then could do this easily because you would just meet up. So you and I will meet up on earth. I'll go visit Zeta Reticuli. You want to go to Trappist-1. We take off and go there and then say, we'll meet back in two weeks. We come back two weeks later and it's literally 80 weeks later on earth. But for us, it's only two weeks later. That's how you could do it. And there are not as many nomadic societies on earth now as there used to be, but there still are nomadic societies. In fact, in Southeast Asia,