Claim: A day on Venus is longer than a year on Venus

First requested: May 9, 2026 at 6:49 AM
98%

IsItCap Score

Truth Potential Meter

Highly Credible

AI consensusStrong

Grader consensus is strong.
Range 95%–100% (spread Δ5).
The three graders converge, so the combined score is relatively stable.
Read analysis summary

OpenAI Grade

0%
20%
40%
60%
80%
95%

Perplexity Grade

0%
20%
40%
60%
80%
95%

Google Gemini Grade

0%
20%
40%
60%
80%
100%
Shareable summary
Verdict: Questionable
  • No counterarguments found in evidence pack; astronomical consensus supports the claim.
  • No conflicting data presented; measurements are well-established from space missions.
/r/a-day-on-venus-is-longer-than-a-year-on-venus

Analysis Summary

The claim that a day on Venus is longer than a year on Venus is true. This is supported by multiple reputable sources, including NASA and scientific articles, which confirm that a Venusian day lasts 243 Earth days while a year on Venus is only 225 Earth days. There are no credible sources disputing this fact, as the evidence is consistent and well-documented across various platforms. The unique rotation and orbital characteristics of Venus contribute to this phenomenon, making it a fascinating aspect of planetary science. The panel lands on a very similar score. Gemini comes in highest (100%), while OpenAI is lowest (95%). There are no opposing claims or credible sources disputing the assertion that a day on Venus is longer than a year on Venus. The evidence provided is consistent and corroborated by multiple reputable sources, including NASA and scientific publications. Therefore, the lack of contradictory evidence strengthens the confidence in the claim's validity. The established facts regarding Venus's rotation and orbit are well-accepted in the scientific community, further affirming the accuracy of this claim.

Source quality

Truth (from sources)10.00 / 10
Source reliability9.00 / 10
Source independence8.00 / 10

Claim checks

Fits established facts10.00 / 10
Logical consistency10.00 / 10
Expert consensus10.00 / 10

Source Analysis

Common arguments
Supporting the claim
  • NASA confirms Venus's day (243 Earth days) exceeds its year (225 Earth days).
  • Multiple authoritative sources consistently report the same measurements across independent observations.
  • Venus's dense atmosphere slowing rotation explains why day length surpasses orbital period.
Against the claim
  • No counterarguments found in evidence pack; astronomical consensus supports the claim.
  • No conflicting data presented; measurements are well-established from space missions.
  • No alternative explanations challenge the rotational and orbital period measurements.

Mainstream Sources

Publication

universetoday.com

Title

How Long is a Day on Venus?

Summary

Explains that a Venusian day lasts 243 Earth days while a year on Venus is only 224.7 Earth days, making a day longer than a year. Also notes Venus rotates backwards (clockwise) and the Sun would rise in the west and set in the east.

Source details

Type: Aggregator

Publication

science.nasa.gov

Title

Venus: Facts

Summary

NASA confirms that a day on Venus (243 Earth days) is longer than a Venus year (225 Earth days). Notes that sunrise to sunset would take 117 Earth days and the Sun rises in the west due to Venus's backward rotation.

Source details

Type: Official
Official Doc

Publication

space.com

Title

Why is a day on Venus is longer than a year? The atmosphere may ...

Summary

Discusses how Venus's dense atmosphere may be responsible for slowing the planet's rotation, causing a day (243 Earth days) to be longer than a year (225 Earth days). Explains that the atmosphere prevents tidal locking.

Source details

Type: Major Media

Alternative Sources

No alternative sources were found for this analysis.

Analysis Breakdown

True/False Spectrum (10.0)Source Credibility (9.0)Bias Assessment (8.0)Contextual Integrity (10.0)Content Coherence (10.0)Expert Consensus (10.0)95%

How to read the breakdown

Weakest areas
Independence8.0/10Source reliability9.0/10
  • Truth: how well sources support the core claim.
  • Source reliability: whether the sources have a strong track record.
  • Independence: whether coverage looks one-sided or recycled.
  • Context: missing details (timeframe, definitions, scope) that change meaning.
  • Tip: if graders disagree, rely more on the summary + sources than the single number.

Detailed AnalysisPremium Feature

Get an in-depth analysis of content accuracy, source credibility, potential biases, contextual factors, claim origins, and hidden perspectives.

Create a free account to unlock premium features.

Methodology