Why Everything We Perceive Is Always Out of Date

Understanding why what we experience as the present is actually the past.

Posted Nov 25, 2020

When astronomers estimate the distance between the Earth and another astrological entity, they typically talk in terms of light-years. For example, the Alpha Centauri star (that actually comprises three separate stars), is the closest star to Earth other than the sun and is estimated to be 4.37 light-years away. This means that if we were to view Alpha Centauri from the Earth, we would be looking at the star as it was some 4.37 years ago. In other words, it could be said that our view of Alpha Centauri is 4.37 years out of date.

On a much smaller scale, the exact same principle applies when we perceive objects that are closer to us. We see an object because light from the sun (or another light source) is reflected by the object before traveling to the light-sensitive retina at the back of our eyes. When sight receptors are stimulated, electrochemical impulses travel along the nerves via a process of saltatory conduction, and once received by the central nervous system, they are transformed into a coherent image that can be acted upon.

The speed of light is approximately 300,000 kilometres per second (299,792 km/s to be more precise). This means that if we look from the top of a mountain at a lake that is 30 kilometres away, it takes roughly 0.00001 seconds for light from the lake to reach us. Therefore, our view of the lake is ever so slightly out of date. Likewise, if we look at a person standing just three meters in front of us, it takes approximately 0.000000001 seconds for the reflected light to reach us. In fact, it actually takes slightly longer than this because light travels slower through the Earth’s atmosphere than it does through space, and it also takes a brief moment for electrochemical impulses to travel from the eyes and be processed by the brain.

The same principle applies when we hear a sound, except that because sound travels more slowly than light, there is a greater lag time. In dry air at 68 °F, sound travels at approximately 343 metres per second (1,235 km/h), although this varies according to factors such as temperature, humidity, atmospheric pressure, altitude, and wind. Therefore, if we are talking with somebody who is 3.5 meters away, it takes approximately 0.01 seconds for the sound waves carrying their words to reach us, or approximately 0.1 seconds if they are 35 meters away. However, in practice, it’s slightly longer than this because it also takes time for vibrations in the eardrum to travel via the middle ear to the cochlea before triggering electrochemical signals to be sent to the brain via the auditory nerves.

For the average person, such small delays are likely to have minimal (if any) implications in terms of how they go about their day. Also, the human brain is habituated to processing sensory information such that it is perceived as representing real-time, despite the fact that the sources of sensory input may have originated at different time points.

Nevertheless, the fact remains that regardless of whether it’s a delay of a fraction of a second or several years, our sensory perceptions are always out of date. This means that while the brain gives the impression things are happening in the present, we only ever perceive the past.

“Living in the present moment” or “being in the here and now” appear to have become buzz phrases in recent years, perhaps because of the influence of the popular mindfulness wellbeing trend. However, from a certain point of view, it could be argued that individuals practising mindfulness are actually (slightly) behind the times!

Perhaps this is why scientific interest in contemplative psychology appears to be extending beyond mindfulness to include exploring ancient wisdom principles such as “emptiness,” “non-duality,” and “impermanence,” which are concerned with eliciting insight into the true nature by which perception and reality operate.


Mendelson, K. S. (2006). “The story of c”. American Journal of Physics, 74, 995-997.

Penrose, R. (2004). The Road to Reality: A Complete Guide to the Laws of the Universe. Vintage Books.

Schaefer, B. E. (1999). Severe limits on variations of the speed of light with frequency. Physical Review Letters, 82, 4964-4964.

Shonin, E., & Van Gordon, W. (2013). Searching for the present moment, Mindfulness, 5, 105-107.

Torres, C. A. O., Quast, G. R., da Silva, L., de la Reza, R., Melo, C. H. F., & Sterzik, M. (2006). Search for associations containing young stars (SACY). Astronomy and Astrophysics 460(3): 695–708

Van Gordon, W., Shonin, E., & Griffiths, M. D. (2017). Buddhist emptiness theory: Implications for psychology. Psychology of Religion and Spirituality, 9, 309-318.

Wiegert, P. A., & Holman, M. J. (1997). The stability of planets in the Alpha Centauri system. The Astronomical Journal, 113, 1445-1450.