SCOTT DETROW, HOST:
Here on Earth, we take for granted the fact that my watch displays the same time as everybody else's watch does, at least within my time zone. And when you step back and think about it, it is kind of amazing that the whole world can sync up our clocks like that. But it is a lot more complicated to sync up a clock here on Earth with, say, a clock on Mars. And that is because time passes differently, depending on where you are in the universe, and depending on the gravitational field you're in. Luckily for us, physicists at the National Institute of Standards and Technology have done the math, so we don't have to, and they have figured out just how much faster a clock ticks on Mars. Bijunath Patla is the coauthor of a paper all about that out this month in The Astronomical Journal and joins me now. Welcome to ALL THINGS CONSIDERED.
BIJUNATH PATLA: Thank you for having me on.
DETROW: Let's just get right to it. How much faster do clocks tick on Mars than Earth?
PATLA: The clocks on Earth on average will tick 477 microseconds per day faster than clocks on Earth.
DETROW: How can I even begin to think of a microsecond?
PATLA: This is a millionth of a second, and it's approximately the time it takes light to travel 300 meters.
DETROW: OK. So why is it? I mean, I generally understand the concepts of why time is relative in different places, but why is it exactly that a clock is going to go faster on Mars than Earth?
PATLA: So the distance from the sun of Mars is way greater than it is on Earth. As you go farther out into the solar system, the gravitational pull of the sun decreases dramatically. And therefore, since Mars is farther out than the Earth, the gravitational pull of the sun is much lesser, and therefore, the clocks are going to tick faster.
DETROW: So I think Einstein's theory of relativity is, like, a pop culture thing that people at least know the phrase, if not the details, the general idea that gravity affects the passage of time. I'm wondering, do these calculations that you've been working on - do they add anything to that conversation? Is there something new here to think about and learn more about?
PATLA: This calculation provides a framework where we can test general relativity within the inner solar system because there is a general consensus within the community that quantum mechanics and general relativity are incompatible. And this kind of clocks on different planets would allow us to put constraints on the limitations of general relativity, or to check whether is there any fundamental connection between quantum mechanics and relativity.
DETROW: I find this really interesting. I like Mars. I like the general idea of space-time. But is there a practical use for this, or is this one step towards something very practical for the scientific community to have a better sense of now that you figured this out?
PATLA: The practical aspect comes from, if you want to translate the communication infrastructure that we have on Earth to Mars, then we'll have to have the clocks synchronize pretty accurately. If you want to have multiple robots and scale up the operation, then the robots have to talk to each other. And therefore, we'll have to have a different way to communicate. And that's where the calculation comes into play if we are envisioning to becoming an interplanetary species.
DETROW: That is Bijunath Patla, a theoretical physicist at the National Institute of Standards and Technology. I know that right now, at least, we're just talking Earth to Earth, but I enjoyed the conversation. Thank you so much.
PATLA: Thank you. Transcript provided by NPR, Copyright NPR.
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