What is time? Is time travel possible? Today, we know that time travel indeed exists beyond myths, science fiction, and Hollywood movies. According to Stephen Hawking, time travel is possible, and not just in the way we might think. Backward time travel is not supported by Hawking’s theories, because new matter (a new you) would need to be created – one existing in the past and one in the present, traveling back in time. This doesn’t hold up, because matter cannot be created. However, time travel to the future is possible if gravity warps the space-time continuum. Anytime you climb a mountain, fly in a jet from place to place, or even ride in an elevator, you alter the speed at which you get to the future because you are encountering a change in gravity’s pull. Time goes faster when there is less gravitational force at play.
Will we ever have the technology to travel forward, or even backward, in time? It is nearly impossible to predict what future technology might be discovered to help us time travel. History is full of many examples showing how humans have underestimated technology and what it can do:
"The telephone has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us." (Western Union internal memo, 1876)
"There is no reason for any individual to have a computer in their home." (Ken Olsen, president, chairman and founder of Digital Equipment Corp., 1977)
Science fiction helped prompt humans to travel to our nearest neighbor in space – the Moon. Perhaps science-fiction stories about time traveling will inspire humans to develop the technology to make time-travel possible…
In this lesson, students will watch and discuss ideas from the Can We Time Travel? episode of Genius. They will discuss specific points and ideas from the video with each other as a whole and/or in collaborative groups. Students will then work in collaborative groups to choose selections from at least two media selections (video or books) supporting whether they believe time travel is possible, giving evidence for or against. They will obtain information, evaluate it and communicate what they have found. All students will participate as active speakers and listeners; both the typically quiet and active speakers will have equal footing. Organized and deliberate classroom discussions can help students practice the skills of the Scientific and Engineering Practices engaging in argument from evidence and obtaining, evaluating, and communicating information from the Next Generation Science Standards (NGSS). Engagement in these practices is language intensive and requires students to participate in classroom science dialogue.
3-5 class periods
Understand the nature of time and the possibility of time travel by engaging in collaborative dialog with peers.
Genius episode 101 – Can We Time Travel? (click to watch)
Specific time clips from as follows, if needed:
"Traveling to the Future – Black Holes"
"Can we Really Time Travel? Gravity and Time"
"Black Holes and General Relativity"
In: 01:32:29:00 (approx.)
Out: 01:42:59:06 (approx.)
"How Earth’s Gravity Affects Time"
In: 01:43:15:21 (approx.)
Out: 01:52:26:10 (approx.)
Introduce the episode Can We Time Travel? to students, explaining that they will be using the information from this video, along with other resources, to engage in argument from evidence about the feasibility of time travel.
Use the following discussion questions to stimulate conversation both before and after viewing. Consider pairing or grouping students together to discuss and answer specific questions, presenting their view, opinions, and facts to their peers. You may want to give the discussion questions to the students during viewing.
Before Viewing for Entire Class:
- Have you ever wanted to visit a different age than the one you are living in now? If so, what time period? Why that one? What would you expect to be very different from the time you are living in now?
- What is time?
After viewing in small, collaborative groups:
1. Have groups discuss the following questions:
- Have students consider this quote from physicist Stephen Hawking: "Time travel might be possible, but if that's the case why haven't we been overrun by tourists from the future?" (If the unlikelihood of traveling backward through time is considered, then people from the future would not be found in our time because this means they would have traveled backwards through time).
- Why did Norman, Marisol and Paul miss the party once they found the location from the 3 numbers they were given? What was missing? (They were missing the 4th dimension, TIME! Three numbers are needed to describe a place, but you need a 4th to describe an event – TIME!)
- Hawking states that backwards time travel is unlikely to work. Why is this? (Traveling backward in time means you will always see yourself as you travel ‘back’. The Laws of Nature do not support the new creation of matter as a person travels backward in time, seeing themselves in the past when they also exist in the present.)
- What was unique about the way Einstein viewed space and time? (Einstein noted that time and space are not independent of one another – they are parts of the same thing, making up the fabric of space-time. You cannot separate space from time. They do not exist separately.)
- The warping of space-time is what creates gravity and alters time itself. What happens to time as it is affected by gravity of different strengths? (Time is altered – the affect is intensified as gravity increases. This is the Theory of General Relativity. Time slows as it nears a black hole with its massive amounts of gravity. Time is stretched out…slows down.)
- What happens to time as a person travels higher and higher on earth, compared to someone at ground- or sea-level? (Time passes more quickly due to there being less gravity which can slow down time. The further you are from the center of the earth where gravity is at its greatest, the faster time will go.)
- Scientists and engineers must rely on data to supply the evidence behind their claims. What evidence supported Norman and Marisol’s time travel claim to the future in Can We Time Travel? (The two Cesium clocks, one left at ~2300 ft. and the other brought to ~9000 ft., showed time travel had occurred after 24 hours. The clock under less gravitational force, on top of the mountain at ~9000 ft., went faster than the one under more gravitational force, the one left at ~2300 ft. The difference was only 20.485 nanoseconds but when Paul left the 2300 ft. level and traveled up the mountain to Norman and Marisol at 9000 ft. 24 hrs. later…he time traveled to the future!)
2. Questions for further discussion. After sharing the students’ answers to these discussion questions, assign some or all of the following questions to small groups of students. Give the students adequate time to develop their answers (during class or as a homework assignment) and share their answers with each other through tools such as Google Docs or in a large-group share.
- How does popular media portray time travel in science fiction literature and movies? (Answers will vary…)
- Why do you think time travel is such an appealing subject, based on its popularity in books and movies for many, many years? (Answers will vary…)
- What are several specific difficulties that time travel presents? (Answers will vary…but the following are the general basis for most of the difficulties: traveling to the past would require new matter to be created – a new ‘you’ – one in the present traveling to the past and one already in the past being viewed by…you. According to the Laws of Nature, this is not possible. Traveling to the future would require manipulating and dealing with massive amounts of gravitational differences to warp the space-time continuum, perhaps only made possible by technology not invented as yet.)
- If you travel to the past and alter an event that is happening or about to happen which involves you personally, how would that affect you in the present…and in the future? (Answers will vary…)
- Would it be easier to time travel back through time or forward through time? Based on the Genius Episode Can We Time Travel?, which would be more feasible and why? (According to Stephen Hawking, backward time travel is most unlikely because new matter (a new you) would need to be created – one of you existing in the past and one in the present traveling back in time. New matter cannot be created. Time travel to the future could be possible if gravity is used to warp the space-time continuum.)
3. Engaging in argument from evidence. In their small, collaborative groups, have the students choose at least two movie time clips from the Genius Episode Can We Time Travel? (listed above) which support or refute the possibility of time travel. Alternatively, beforehand you can choose a selection of time clips from the Can We Time Travel? episode showing various aspects of time travel and have each collaborative group choose which ones they want to work with. Students will work together, either in class or via online using Google Docs, etc., to answer the following from their chosen clips:
- What is a unique challenge that affects whether time travel can occur? Is the problem solvable? If not, why not? (An example of a unique issue could be traveling to the past, which Hawking believes is impossible. Other unique problems could be any that were presented in the film, including the need for massive amounts of gravitational pull to make future time travel even remotely possible. Several other key problems are discussed in the Can We Time Travel? episode. Students may use other research they have done to support or refute the possibility of time travel as long as they use at least two clips from the episode Can We Time Travel.)
- How do these clips present or include discussion/ investigation of the space-time continuum?
- Present a final argument using evidence from chosen clip(s) to either support or refute time travel. Be specific with evidence by referring back to clips and outlining the evidence for or against.
- Ask peers whether they have any questions, and engage in a discussion if relevant to conclude the presentation.
4. Follow-up activity. After the students present their final argument to their peers, discuss what the presentations had in common. Do most students see time travel possible? Why or why not? What were common ideas, problems, or solutions in most of the presentations?
Optional Lesson - Time Paradox
1. Discuss with students that one of the complications with time travel is an idea known as the "grandfather paradox." Stated simply, it says that if you traveled to the past and accidentally killed your grandfather before your parents are conceived, there would be no way for you to be born. Therefore, you would not exist to travel back in time in the first place. So how could you have killed your grandfather?
2. Have students develop their own scenario where they go back in time and change something. Have the students list the many ways they think their change might affect a future timeline.
3. Have the students present their scenario to their peers.
4. Consider having the students engage in argument as to whether a scenario is at all feasible and to state the evidence they might have to support that argument.
For more information on this optional lesson, visit NOVA Online "Measuring Time" lesson plan.
Students interested in further exploring the topic of time travel can check out the following books and movies:
The Chronos Files by Rysa Walker,
Ancient Guardians by S.L. Morgan,
The Earth and Sky Trilogy by Megan Crewe,
The Transcend Time Saga by Michelle Madow,
A Wrinkle in Time by Madeleine L’Engle,
Rip Van Winkle by Washington Irving,
A Christmas Carol by Charlies Dickens,
The Time Machine by H.G. Wells,
Outlander by Diana Gabaldon,
Harry Potter and the Prisoner of Azkaban by J.K. Rowling,
11/22/63 by Stephen King,
Dr. Who series by Godon Flemyng
Movies and TV shows:
Films in the Star Trek Franchise, including:
- Star Trek (2009) by J.J. Abrams,
- Star Trek: Ismael (1985),
- Star Trek IV: The Voyage Ho me
- Star Trek Generations
- Star Trek: First Contact
Dr. Who series (movie or tv series)
Planet of the Apes movie series,
Twilight Zone: The Movie
Back to the Future movies
Bill & Ted’s Excellent Adventure